The subject matter disclosed herein relates to the art of helicopters and, more specifically, to a helicopter rotor control system.
Control of rotary-wing aircraft is effected by rotor blade pitch variations. Rotor blades are controlled individually (cyclic control) and collectively (collective control). Main rotor pitch control is typically achieved through a swashplate assembly that transfers motion of non-rotating control members to rotating control members. The swashplate assembly is typically concentrically mounted about a rotor shaft. A typical swashplate assembly includes two rings connected by a series of bearings. One ring is mounted to the aircraft (stationary) and another ring is mounted to a hub portion of the rotor shaft (rotating). Movements in the stationary ring are transferred to the rotating ring to control blade pitch.
Rotary-wing aircraft having dual or counter-rotating rotor blade systems require both an upper rotor control system and a lower rotor control system. The lower rotor control system utilizes a conventional swashplate assembly mounted about a lower control rotor shaft. The upper rotor control system is typically more complex and utilizes an upper rotor control shaft mounted through the lower rotor shaft. The upper rotor control system includes an upper rotor swashplate assembly, a motion multiplier, and long control rods located inside the upper rotor control shaft. The long control rods are formed of a relatively heavy, large diameter material that is resistant to buckling forces generated by blade pitching loads in the upper rotor. The heavy large diameter rods add weight to the upper control system and are difficult to package within the upper rotor control shaft.